Apparatus for shunting of track circuits



May 2, 1939. THQMPSQN 2,156,710

APPARATUS FOR SHUNTTNG OF TRACK CTRCUTTS Filed June 14, 1932 INVENTOR Howapa'A. 77202408012.

BY QQW- H16" ATTORNEY Patented May 2, 1939 PT ET UFFICE APPARATUS FOR SHUNTING 0F TRACK CIRCUITS 'Howard A. Thompson, Eolgcwood, Pa, assignor to The Union Switch & Signal Qompany, Swissvale, Pa, a corporation of Pennsylvania Application June 14, 1932, Serial No. 617,137

18 Claims.

My invention relates to apparatus for shunting of track circuits, and more specifically to- -apparatus for shunting ofrailway track circuits by rail vehicles having wheels which do not make dependable electrical contact with the rails, or are completely insulated therefrom by non-conducting tread material.

, I will describe several forms of track circuit shunting apparatus embodying my invention, and will then point out the novel features thereof in claims.

The apparatus for shunting of track circuits set forth inmy present application is somewhat similar tothat set forth in my copending ap- .plication-Serial No. 629,030, filed on August 16, 1932, for Apparatus for decreasing rail contact resistance, and the said copending application contains claims which cover broadly certain features of the invention described in my present application.

In the accompanying drawing, Fig. 1 shows in elevation a rail vehicle equipped with the car carried portion of the apparatus embodying my invention. Fig. 2 is a diagrammatic View showing an alternating current track circuit equipped With-the wayside portion of the apparatus embodying my invention, and also showing a part of the car-carried equipment illustrated in Fig. 1. Fig. 3 is a diagrammatic View showing a modification of the apparatus illustrated in Fig. 2. Fig. 4 is a diagrammatic view showing the application of my invention to a direct current track circuit.

Similar reference characters refer to similar parts in each of the several views.

. Referring to Fig. l of the drawing, the ref- ;erence character A designates a rail vehicle in which the sets of wheels l and 2' do not make electrical contact with the rails, said wheels having pneumatic tires, or being equipped with any other suitable insulating tread material. Mounted-upon car A is a direct current generator G, drivenby a motor M. As more clearly illustrated in Fig. 2, one terminal of generator G makes contact with one rail of the track by means. or a brush 3, and the other terminal of generator G makes contact with the remaining rail by means of a brush i, through a current limiting resistor R. Connected across a por tion of ,resistorB. is an indicator L, of any suitable type, for indicating that the current developed by generator G is being passed into the rails of the track.

The apparatus so far described provides a irrethodfor superimposing a direct current from a source aboard a rail vehicle, upon the rails A of the track, and for checking that the superimposed current is actually being conducted into the rails. The manner in which the superimposed current becomes effective to shunt the track circuit will be apparent from a description of the remaining figures of the drawing.

Referring to Fig. 2, the stretch'of track shown therein is divided by insulated joints 5 to form alternating current track circuit sections of the. usual type, one such section E-F being illustrated. Track circuit energy for a track relay D connected at one end of section EF. is supplied from a track transformer T connected at the other end of the section, througha current limiting reactor Q. Instead of connecting the secondary winding of transformer T directly withthe rails, through the reactor Q, as is common practice in connection with heavy rolling stock of the usual steel-Wheeled type which, in itself provides satisfactory shunting, I interpose an auxiliary transformer T between the track transformer T and the track, interposing also a second auxiliary transformer-T between the track relay D and the track.

The secondary windings 6 and 8 of transformers T andT respectively, are constructed of heavy wire in order toprovide a low resistance path for the flow of-direct current from generator G, and thenumber'of turns in windings 6 and" 8 is so chosen that the current from generator G passing through these windings will readily saturate the cores of the respective transformers. For examplaassuming that car A occupiessection E-F of Fig. 2, direct current of the proper magnitude will flowthrough wind ing 5 of transformer T saturating the core of this transformer, thereby. preventing the effective transfer of alternating current energy from the primary winding of transformer T to the track circuit. As a consequence, track relay D will become deprived of energy, and will release front contact Hi to provide a suitable danger signal for following trafiic. The reactor Q will limit the current supplied by track transformer T when the core of transformer '11 becomes saturated.

Simultaneously with the saturation of the core of transformer T direct current from generator G will also flow through winding 8 of 50 transformer T saturating the core of this transformer also, to deprive relay D of any remaining energy which might continue to be furnished through transformer T due to imperfect saturation. It will now be apparent that 5 I have provided a positive method for deenergizing track relay D during the occupancy of section EF by car A. The relative magnitude of the saturation current flowing in windings 6 and 8, will, at any particular time, depend upon the position of car A within the section, which determines the length of rail path over which this current must flow to reach the respective windings.

The brushes 3 and 4 to which the output of generator G is connected should preferably be of sufficient width to bridge the gap formed by an insulated rail joint 5, and these brushes can be arranged in line with each other at right angles to the track, in order to avoid the possibility of their coming to rest simultaneously upon two staggered rail joints. Furthermore, if desired, each brush 3 and 4 can be replaced by a pair of brushes spaced in such manner that the distance between the brushes of each pair will be slightly greater than the stagger distance of the insulated rail joints. If this is done, a narrow brush can be used, and rail contact will be insured, irrespective of the rail joints. It will be obvious that instead of the brush contact provided by brushes 3 and 4, a rolling wheel contact, or any other suitable form of contact can be used as well. Also, in place of the motor driven generator G, any suitable accumulator of electric energy such as a storage battery carried upon car A can be used.

In case an ordinary steel-wheeled car enters upon section E-F of Fig. 2, the shunt provided by the wheels and axles of such a car will re lease relay D, in the ordinary manner. Moreover, should the insulating tread material of the wheels of car A wear away, so that the wheels make electrical contact with the rails. an ordinary wheel and axle shunt will be formed thereby to aid in releasing relay D, and the current supplied by generator G as a result of the wheel and axle short circuit path will not be excessive, being limited by resistor R.

Referring now to Fig. 3, in addition to the transformers T and T I have shown therein a pair of saturation transformers T and T connected directly into the rail circuit. The principle of operation of the apparatus in this figure is the same, in so far as the shunting feature is concerned, as that applying to the apparatus of Fig. 2. Transformers T and T may have a one to one transformation ratio, the primary winding 9 of transformer T being on the same core as the secondary winding I0, and similarly for transformer T The mid-point of winding 9 of each transformer is connected to the midpoint of winding N) by a conductor l8, for a purpose to be explained hereinafter, the rail circuit being broken between windings 9 and H] by the insulated rail joints 5.

When the car A occupies the portion of section EF between transformers T and T direct current from generator G will pass through winding IU of transformer T and will saturate the core of this transformer so that the alternating current supplied by transformer T will not pass effectively beyond winding 9 of transformer T thus depriving relay D of energy. Furthermore, the passage of direct current through winding 8 of transformer T will saturate the core of this transformer also, decreasing further the possi bility of relay D remaining energized. When the car occupies a position between point E and transformer T or a position between transformer T and point F, windings I and 8, or

windings 9 and 6 respectively, will carry the saturating current, so that relay D will be deprived of current in each case. The reason for providing the connector is is to obtain protection against the failure of an insulated joint associated with transformers T and T because, should such failure occur, one half of winding 9 will be short circuited upon the corresponding half of winding ID with the result that the increased current drawn from transformer T in consequence of the above short circuit will result in an abnormally high voltage drop across reactor Q, leaving insufficient voltage across the rails to maintain relay D energized.

One advantage resulting from the use of transformers 'I and T is that when a sufficient number of these transformers is used per track circuit, the length of rail path required for the saturating current from generator G to traverse is decreased, thereby decreasing the resistance of the path and economizing the voltage output of generator G. The current output will not be in creased through the use of the rail transformers T and T because at any one time, but two transformers will carry the saturating current, irrespective of the position of the car in the section, and this represents the same current requirement as exists in Fig. 2 wherein the rail transformers are not used.

Referring to Fig. 4, the track circuit of this figure is supplied with direct current from a source 13, through a limiting resistor K, to operate a direct current polarized relay P connected to the rails at the other end of the track section. When section EF is unoccupied, relay P will be energized with current of normal relative polarity, as determined by the connections of battery B to the rail circuit, so that front neutral contact ll of relay P will be closed, and polar contact 13 of this relay will occupy its left-hand position, thereby closing an energizing circuit for lamp V of signal S, which may be traced from one terminal N, iront contact H of relay P, wire l2, polar contact 53 in the left-hand position, wire I1, and lamp V to the other terminal 0 of the same source. The manner in which relay P becomes energized from battery B after the car has left section E-F is as follows: As the car leaves point F, the polarity of the current supplied to relay P will be reversed, and this will cause the momentary release of the neutral armature of this relay. Neutral back contact 20 will therefore be momentarily closed, thereby closing the normal energizing circuit for the relay over wires 22, 23 and 24. Immediately thereafter, contact 20 will open due to the pick-up of the neutral armature, but before this occurs, polar contact 2| will be swung to the left, maintaining the energizing circuit for relay P over wires 25 and 26.

Assuming now that car A occupies section EF, the current applied to the rails from generator G will be of the opposite polarity to that established by battery B, and of sufiicient strength to pole change relay P, whereupon an energizing circuit for lamp U of signal S will become closed to provide a restrictive indication, this circuit extending from one terminal N, front neutral contact H of relay P, wire 12, polar contact l3 in the right-hand position, wires I4 and I5, and lamp U, to the other terminal 0 of the same source.

Due to the fact that it is desirable to maintain the current output of generator G at a fixed Value for both alternating and direct current track circuits, in order that the same car can be operated over both types of track circuits without adjustment, it maybe necessary to protect the winding of relay 1? against damagefrom overheating when-the car occupies section E-F. For this purpose, I have provided a resistor H which becomes connected over polar contact 2| in the right-hand position, to limit the current through relay P at such time only when section is occupied by car A. Should relay P belarity-from its respective track battery.

In case it is desired to operate car A over track circuits of either the alternating or the direct current type, the saturation transformers T T T and 'I as well as the polarized relay P can be so designed that each will become operative at one and the same value of current delivered by generator G, so that no adjustment will be required upon car A, when changing from one type of track circuit to the other.

For shunting alternating current track circuits, such for example as are illustrated in Figs. 2 and 3, it is not necessary that generator G be of the direct current type, because, if the track relay D is designed to be frequency selective, generator G may supply alternating current of a frequency sufficiently low as compared with the track circuit frequency to produce the desired saturation effects in transformers T T T or T From the diagram of Fig. 4, it will be apparent that the use of a saturation transformer is not essential in the practice of my invention. Also, the generator G of Fig. 4 need not be of the direct-current type, as a low frequency alternating current generator can be used, provided the polarized relay P is so designed that polar contact l3 will follow the alternating current pulses, thereby giving a distinctive indication when the track circuit is occupied by car 'A. Similarly,

the saturation transformers of Figs. 2 and 3 can also be eliminated if the output of generator G is alternating current of a frequency differing slightly from the frequency of the track circuit supply, so that a beat note will be produced, the track relay D being so designed that contact l9 will follow the beat note pulses, thereby giving a distinctive indication of the occupancy of the track circuit by car A.

Although I have herein shown and described only a few forms of apparatus for shunting of track circuits embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of railway track divided into track circuit sections, a track transformer and a track relay for each section, two saturation transformers for each section one connected between said track transformer and the track and the other connected between said track relay and the track, a rail vehicle having a source of direct current thereon, and means for conducting current from said source to the rails of said track for saturating the cores of said saturation transformers whereby the energy flowing from said track transformer to said track relay will be decreased sufficiently to release said track relay.

2. In combination with a stretch of railway track divided into track circuit sections, a source of alternating current track circuit energy and a track relay for each section, a saturation transformer for each section connected between said alternating current source and the track, a rail vehicle having a source of direct current thereon, and means for conducting current from said direct current source to the rails of said track for saturating the core of said transformer whereby the track circuit energy flowing to said track relay is decreased sufficiently to release the track relay.

3. In combination with a stretch of railway track divided into track circuit sections, a'source of alternating current track circuit energy and a track relay for each section, an insulating transformer of the saturation type for each section interposed between said alternating current source and said track relay, a rail vehicle having a source of direct current thereon, and means for conducting current from said direct current source to the rails of said track for saturating the core of said transformer whereby the track circuit energyflowing to said track relay is decreased sufficiently to release the track relay.

4. In combination with a stretch of railway track divided into track circuit sections, a source of alternating current track circuit energy and a track relay for each section, an insulating transformer of the saturation type for each section interposed between said alternating current source and said track relay, a rail vehicle having a source of current thereon of substantially lower frequency than said track circuit frequency, and means for conducting current from said rail vehicle source to the rails of said track for saturating the core of said transformer whereby the track circuit energy flowing to said track relay is decreased suficiently to release the track relay.

' 5. In combination with a stretch of railway track divided into track circuit sections, a source of track circuit energy and a track relay for each section, an insulating transformer of the saturation type interposed between said track relay and the track, a rail vehicle having an auxiliary source of direct current thereon, a current limiting impedance having one terminal connected with one terminal of said auxiliary source, an indicator connected across a portion of said impedance for indicating the flow of current from said auxiliary source, and means for conducting current from the other terminal of said auxiliary source to one rail of said track and from the other terminal of said impedance to the remaining rail of said track for saturating the core of said transformer whereby the track circuit energy flowing to said track relay is decreased sufficiently to release the track relay.

6. Apparatus for improving the shunting of a track circuit comprising, in combination, a primary source of track circuit energy, a track relay, an insulating transformer of the saturation type interposed between said primary source and said track relay, an auxiliary source of saturation current, and means for applying a potential from said auxiliary source across the rails of the track circuit for causing a saturating current to flow in one Winding of said transformer to saturate the core thereof, thereby impeding the transfer of track circuit energy from said primary source to said track relay for causing said track relay to release.

7. In combination with a stretch of railway track divided into track circuit sections, a primary source of direct current track circuit energy and a polarized track relay for each section, a rail vehicle having an auxiliary source of direct current thereon, and means for impressing a potential of sufiicient magnitude from said auxiliary source across the rails of the track circuit in a direction such as to oppose the potential of said primary source whereby said track relay will become pole changed by current from said auxiliary source to indicate the occupancy of the track section by said vehicle.

a 8. In combination with a section of railway track, a resistor, a polarized track relay connected across the rails of said section in series with said resistor, a source of direct current track circuit energy connected across the rails of said section for energizing said track relay in one direction, a rail vehicle provided with means for impressing across the rails of said section an electromotive force which causes the energization of said track relay in the opposite direction, and means for shunting said resistor when said track relay is deenergized or is energized in said one direction.

9. In a railway block signaling shunt system of the character in which a signal is maintained by an energized relay associated with a block and electric current is supplied to the relay through the tracks and shunted by wheels and axle of a car in the block; means for insuring operation of the relay by a lightweight car in the block, which comprises a source of electric potential carried by the car, current conductors connecting the positive and negative sides of the said car source respectively with the negative and positive sides of the track circuit between the relay and track source of current supply, and means in circuit with the car carried source of potential for regulating the amperage fiow and voltage of the current introduced into the rails.

10. In combination with a section of railway track and a rail vehicle thereon, a track circuit source of current for said section, a track relay energized by current from said source, an auxiliary source of current on the vehicle, and means for impresing a potential from said auxiliary source across the rails of said section in a direction to oppose the energization of the track relay from said track circuit source to thereby aid the release of said track relay.

11. In combination with a section of railway track, a track relay, means for supplying current to the rails of said section for energizing said track relay with current of a given relative polari ty, and vehicle-carried means for supplying an auxiliary current of opposite relative polarity tothe rails of said section for substantially neutralizing the energization of said track relay to aid the release thereof.

12. In combination with a section of railway track, a track relay, means for supplying a first current to the rails of said section for energizing said track relay, and vehicle-carried means for supplying a second current of different character to the rails of said section for neutralizing the eiTect of said first current in the track relay to aid the release thereof.

13. In combination with a section of railway track, means for supplying periodic current to the rails of said section, means including a magnetizable device having a winding traversed by the current supplied to said section, a track relay receiving current from the rails of said section, and means effective when said section becomes occupied for supplying an additional current to the winding of said device for controlling the efiective impedance thereof to thereby control the current received by said track relay.

14. In combination with a section of railway track, a source of periodic current, means includ ing a device comprising a saturable core and a winding for supplying current from said source to the rails of said section, a track relay receiving current from the rails of said section, and means effective when said section becomes occupied for supplying a saturating current to said winding for controlling the effective impedance of said device to thereby control the current received by said track relay.

15. In combination with a section of railway track, a source of periodic current connected across the rails of said section, a track relay receiving current from the rails of said section, a saturable core device interposed between said relay and said rails, and meeans eiTective when said section becomes occupied for supplying a saturating current to said device for controlling the effective impedance thereof to thereby control the current received by said track relay.

16. In combination with a section of railway track, a source of periodic current, means including a first saturable core device for supplying current from said source to the rails of said section, a track relay receiving current from the rails of said section, a second saturable core device interposed between said relay and said rails, and means efiective when said section becomes occupied for supplying a saturating current to said first and second devices for controlling the effective impedances thereof to thereby control the current received by said track relay.

17. In combination with a section of railway track and a rail vehicle incapable of completing a conducting path from one to the other rail of the track, a track circuit for said section comprising a primary source of track circuit energy and a track relay connected therewith, and means for applying a potential from an auxiliary source carried on said rail vehicle across the rails of said track circuit to cause a response of said track relay thereby indicating the presence of said rail vehicle upon said track circuit section.

13. In combination with a section of railway track, a track relay, means for supplying a first current to the rails of said section for energizing said track relay, and means carried upon a vehicle incapable of shunting the track circuit for supplying a second current of different character to the rails of said section for rendering said first current inefiective to energize the track relay whereby said track relay will release.

HOWARD A. THOIVIPSON. 

